1. Field of the Invention
The present invention relates to the field of forming glass patterns on a substrate, and more particularly to precise patterning of thin glass films for planar optical devices.
2. Technical Background
Structures incorporating patterned glass films are utilized in planar optical devices, dielectric layers in semiconductors, barrier structures in plasma-addressed electro-optic display panels (commonly referred to as xe2x80x9cPALCxe2x80x9d display devices), biochemical sensors, and other devices. The lack of anisotropic etching makes patterning of glass thin film structures difficult. For example, planar optical structures compatible with optical fiber based technology require deposition and patterning of relatively thick (e.g., from about 5 to about 8 micrometers) films of uniform thickness with precisely defined sidewall geometry to form planar waveguides. Currently, these planar optical devices are typically patterned by either dry etching or ion-exchange. Dry etching is slow and expensive, and waveguides prepared using ion-exchange techniques are typically anisotropic in shape which leads to optical polarization dependence.
Photosensitive lithium silicate, barium silicate, and lithium barium silicate glasses which contain nucleation agents such as Ag and CeO2 and sensitizers such as F, permit chemical machining of glass structures. Irradiation with UV, X-rays, or an electron beam produces noble metal nuclei which serve as sites for epitaxial growth of needle-like lithium disilicate or barium disilicate crystals upon heat treatment. In the case of lithium silicates, chemical machining of highly anisotropic structures is possible because the etch rate in dilute HF is 10 to 50 times greater in the crystalline phase compared to the remaining glass. However, conventional techniques of patterning photosensitive glasses are not suitable for submicron scale patterning in planar applications because the size of the lithium or barium disilicate is typically about 5 microns in the longest dimension.
Accordingly, relatively facile and less expensive techniques of forming patterned glass films having submicron features are highly desired.
This invention provides a relatively facile and relatively inexpensive method of precisely patterning glass films having submicron size features and resulting product.
The method of forming a glass pattern on a substrate in accordance with the present invention involves the steps of depositing a layer of a crystallizable glass on a substrate, and forming a patterned seed layer including a nucleating agent on a major planar surface of the crystallizable glass. The patterned seed layer may be formed on the substrate first, and the layer or crystallizable glass may be subsequently deposited over the patterned seed layer and exposed portions of the substrate which are not covered with the patterned seed layer. Alternatively, the layer of crystallizable glass may be deposited on the substrate first, and the patterned seed layer may be subsequently formed on the layer of crystallizable glass. Thereafter, the patterned seed layer and the layer of crystallizable glass are heat treated to convert selected portions of the crystallizable layer of glass into a crystalline material. The selected portions of the crystallizable layer which are converted to crystalline material correspond to the pattern of the seed layer. Thereafter, the crystalline material is etched to form a desired glass pattern.
Additional features and advantages of the invention will be set forth in the detailed description which follows and will be apparent to those skilled in the art from the description or recognized by practicing the invention as described in the description which follows together with the claims and appended drawings.
It is to be understood that the foregoing description is exemplary of the invention only and is intended to provide an overview for the understanding of the nature and character of the invention as it is defined by the claims. The accompanying drawings are included to provide a further understanding of the invention and are incorporated and constitute part of this specification. The drawings illustrate various features and embodiments of the invention which, together with their description serve to explain the principals and operation of the invention.